1. Field of the Invention
The present invention is generally related to a lubrication system for a marine engine and, more particularly, to a system in which an oil scraper, or oil deflector, is located in the cylinder block portion of a crankcase to remove oil from the proximate rotating surfaces of a crankshaft and connecting rod.
2. Description of the Related Art
Oil that is used to lubricate sliding surfaces associated with an engine is eventually drained to a collection reservoir, such as an oil sump. As the oil flows in the region of the crankshaft of the engine, it is moved at relatively high speed in conjunction with the rapidly rotating surfaces of the crankshaft. The presence of liquid oil in the environment within the crankcase can have a deleterious effect on the efficiency of the engine. This is particularly true in marine engines, where a vertical crankshaft may have numerous counterweights and other elements rotating about its center line past which the liquid oil must pass as it flows downwardly toward the oil sump of the marine engine.
U.S. Pat. No. 5,687,686, which issued to Takahashi on Nov. 18, 1997, describes a lubricating system for a four cycle outboard motor. It embodies an improved lubricating system. The lubricating system drains oil from the cylinder head back to the oil tank, in a manner so as to not add to the length of the engine. In addition, an improved crankcase ventilating system is employed that incorporates a simple baffle arrangement for insuring that oil thrown by the crankshaft rotation will not pass through the ventilating passage into the cylinder head or escape from the ventilating system.
U.S. Pat. No. 6,076,495, which issued to Takahashi et al. on Jun. 20, 2000, describes a bearing arrangement for a vertical engine. The crankshaft rotates within a crankcase chamber defined by the cylinder block and a crankcase cover connected thereto. First web members which support half bearings extend from the cylinder block. Mating half bearings are supported by second web members positioned opposite the first web members. An oil flow passage is defined through the crankcase chamber generally opposite the cylinder block from a top end to a bottom end of the chamber. In one arrangement, the oil flow passage comprises individual passages through the second web members. In another arrangement, the oil flow passage comprises a space between an end of the second web members opposite the cylinder block and the crankcase cover. The crankshaft support arrangement allows lubricating oil introduced into the crankcase chamber to flow downwardly from the top end to the bottom end of the chamber for return to an oil reservoir for recirculation through the engine.
U.S. Pat. No. 6,286,476, which issued to Hiraoka et al. on Sep. 11, 2001, describes an engine lubricating system. The crankshaft rotates within a crankcase chamber defined by the cylinder block and a crankcase cover connected thereto. A baffle plate is positioned in the crankcase chamber between the crankcase cover and the crankshaft. At least one oil flow passage is defined through the crankcase chamber from a top end to a bottom end of the chamber. In one embodiment, oil is supplied through a main passage in the crankcase cover and a branch passage through each second crankshaft support members for lubricating the bearings.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
In certain applications of marine engines, it is impractical to provide components within the crankcase cover for the purpose of directing liquid lubricant away from the crankshaft and downwardly toward an oil reservoir, or sump. It would therefore be significantly beneficial if a marine engine could be provided which performs these functions without requiring direct involvement of the crankcase cover. This would allow the strength and stiffness of the crankcase cover to be independent of the potential adverse affects that could result from the necessity of providing oil deflectors and lubricant passages within the structure of the crankcase cover.